It is the purpose of this project to define the role of protein phosphorylation in the action of vasopressin on the toad bladder. Current interests are: 1) The intracellular location and functional characteristics of cyclic AMP dependent protein kinases. 2) The role of phosphoprotein phosphatases in the control of phosphoprotein metabolism. 3) The functional significance of the principal phosphoproteins, particularly their role in transport.